It's a girl! Serena Williams welcomes first child with fiance Alexis Ohanian

Messages of congratulations flooded in for tennis star Serena Williams after the US Open announced the birth of her first child.

The 23-time Grand Slam champion welcomed a baby girl with fiance Alexis Ohanian​ on Friday, after going into labour the day before.

The news was announced by the US Open Tennis official Twitter account, which shared a video message of congratulations to the athlete – containing heartfelt tributes from tennis pros from around the world.

Stacey Allaster, chief executive of the United States Tennis Association said: "Hey Serena, welcome to the best club in the world: motherhood. Can't wait to see you, a mum, and your precious little healthy baby. Congrats!"

Spain's tennis superstar, Rafael Nadal also tweeted: "Congrats Serena!!! So much joy for you!!!"

Vogue also posted a tribute to the new mother and quoted her interview where she said: "Two weeks after we found out (about the pregnancy), I played the Australian Open.

"I told Alexis it has to be a girl because there I was playing in 100-degree weather, and that baby never gave me any trouble. Ride or die. Women are tough that way."

Last month, the 23-time Grand Slam winner hosted a 50s-themed baby shower, with stars such as Eva Longoria, Ciara, Destiny's Child star Kelly Rowland and La La Anthony among the guests.